[jira] [Resolved] (HADOOP-18190) Collect IOStatistics during S3A prefetching

["Steve Loughran (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-18190?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steve Loughran resolved HADOOP-18190.
-------------------------------------
    Resolution: Fixed

> Collect IOStatistics during S3A prefetching 
> --------------------------------------------
>
>                 Key: HADOOP-18190
>                 URL: https://issues.apache.org/jira/browse/HADOOP-18190
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 3.4.0
>            Reporter: Steve Loughran
>            Assignee: Ahmar Suhail
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 4h 10m
>  Remaining Estimate: 0h
>
> There is a lot more happening in reads, so there's a lot more data to collect and publish in IO stats for us to view in a summary at the end of processes as well as get from the stream while it is active.
> Some useful ones would seem to be:
> counters
>  * is in memory. using 0 or 1 here lets aggregation reports count total #of memory cached files.
>  * prefetching operations executed
>  * errors during prefetching
> gauges
>  * number of blocks in cache
>  * total size of blocks
>  * active prefetches
> + active memory used
> duration tracking count/min/max/ave
>  * time to fetch a block
>  * time queued before the actual fetch begins
>  * time a reader is blocked waiting for a block fetch to complete
> and some info on cache use itself
>  * number of blocks discarded unread
>  * number of prefetched blocks later used
>  * number of backward seeks to a prefetched block
>  * number of forward seeks to a prefetched block
> the key ones I care about are
>  # memory consumption
>  # can we determine if cache is working (reads with cache hit) and when it is not (misses, wasted prefetches)
>  # time blocked on executors
> The stats need to be accessible on a stream even when closed, and aggregated into the FS. once we get per-thread stats contexts we can publish there too and collect in worker threads for reporting in task commits



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